odd though, as I heard an mp3 of a song "lifeblood" by Simon Gallup's band before he joined The Cure, The Magspies, and the bassline on it was more complicated and technically demanding than any of the early Cure stuff, so I wonder why Smith would have played instead.

to me Robert Smith's bass playing on The Top album and a couple of tracks on Japanese Whispers sounds looser in the tone and note phrasing than Cure stuff with Gallup credited - but Gallup's bass playing with Fools Dance when he left The Cure for 2 years is similar to his Cure basslines- eg, open string drone chordal stuff, staccato phrasing.